FIELD OF THE INVENTION
Passive restraint systems of the type popularly referred to as airbag systems are increasingly provided in modern motor vehicles because of their demonstrated ability to diminish the extent of injury to vehicle occupants in the event of a vehicle collision. These airbag systems typically rely on the rapid release of a gas into an inflatable cushion, or airbag, when a collision is sensed by a crash sensor. The airbag opens into a space located between the normal position of a vehicle occupant and portions of the vehicle passenger chamber into which the vehicle occupant might be propelled and thereby injured but for the presence of the airbag.
The airbag assembly typically includes a gas generator, often referred to as an inflator, an airbag or cushion, and a housing, often referred to as a module. The module mounts the folded airbag and the inflator in positions whereby the gas generated by the inflator is discharged or directed into an opening provided in the airbag, thereby causing the airbag to inflate and expand into its intended inflated location. The module also provides secure storage for the airbag and inflator. Additionally, it provides means for mounting the assembly in a sturdy and secure location on the vehicle.
Several different types of inflators are used in airbag assemblies. A relatively simple design merely relies on the rapid release of a compressed gas. This design requires a fairly sturdy compressed gas container which results in a relatively heavy assembly. Other inflators rely on the combustion of solid pyrotechnic materials to provide the inflation gas. Still others, known as hybrid inflators, rely on solid pyrotechnic materials to provide a heated gas which is then mixed with a stored compressed gas to provide the inflation gas. Recently, airbag inflators which rely on the combustion of fluid fuels have been introduced. These inflators rely on the combustion, or exothermic dissociation, of a fluid fuel to create a heated gas which usually is then mixed with a stored compressed gas to provide the inflation gas.
Many of the modules, particularly those for use in front of front seat passengers of automobiles, provide a port through which an elongated inflator is inserted and mounted. The inflators used in such modules are designed to be inserted through such port and be firmly mounted in their intended position within the module. The inflators which require multiple chambers along their length, such as the hybrid and fluid fuel inflators which provide a first combustion chamber for combusting the fuel and a second gas storage chamber for containing a compressed inert gas to be mixed with the combustion gases produced in the combustion chamber, have typically been manufactured by welding two cylindrical sections together. The weld creates a relatively uneven weld seam, which, depending on the welding technique used, can be significantly different from the otherwise relatively uniform cross section of the joined sections. Inertial welding is the prevalent welding technique for such joinder used by some manufacturers. The otherwise uniform cross-section is significantly upset when inertial welding is used to join the cylindrical sections. When such inflators are to be inserted into a module through a port the irregularities contributed by the weld seam must be removed to facilitate such insertion. Typically, such removal requires machining of the exterior circumference of the inflator housing. The machining not only adds to the cost of manufacturing the inflator, it can also result in the walls of the inflator having a variable thickness, especially when the two sections are misaligned during the welding process. If the variation in thickness is excessive, it can result in the item being rejected to scrap. Moreover, machining of the inflator can result in ridges which also will interfere with the smooth installation of the inflator in the module.